Series-parallel charge pump with NMOS devices

Abstract

A charge pump having only NMOS devices charges a plurality of capacitors to a parallel charged voltage level by electrically connecting the capacitors in parallel between an input voltage node and a ground by activating a plurality of first NMOS transistor switches and a plurality of second NMOS transistor switches and deactivating a plurality of third NMOS transistor switches. The charge pump then generates a series capacitor output voltage level at a capacitor series output node by electrically connecting and discharging the capacitors in series between the input voltage node and the capacitor series output node by activating the third NMOS transistor switches and deactivating the first NMOS transistor switches and the second NMOS transistor switches.

What is claimed is: 
     
       1. A method comprising:
 charging a plurality of capacitors in a charge pump to a parallel charged voltage level by electrically connecting the plurality of capacitors in parallel between an input voltage node and a ground by activating a plurality of parallel charging switches and deactivating a plurality of series discharging switches; 
 generating a series capacitor output voltage level at a capacitor series output node by electrically connecting and discharging the plurality of capacitors in series between the input voltage node and the capacitor series output node by activating the plurality of series discharging switches and deactivating the plurality of parallel charging switches; and 
 generating a gate-source voltage for each of the plurality of series discharging switches by flowing a current through a plurality of resistors, each resistor of the plurality of resistors corresponding to one of the plurality of capacitors and to one of the plurality of series discharging switches. 
 
     
     
       2. The method of  claim 1 , wherein:
 each of the plurality of capacitors has a high voltage node and a low voltage node; 
 the plurality of parallel charging switches includes a plurality of first parallel charging switches and a plurality of second parallel charging switches; 
 each of the plurality of first parallel charging switches corresponds to one of the plurality of capacitors; 
 each of the plurality of first parallel charging switches is electrically connected between the input voltage node and the high voltage node of the corresponding one of the plurality of capacitors; 
 each of the plurality of second parallel charging switches corresponds to one of the plurality of capacitors; 
 each of the plurality of second parallel charging switches is electrically connected between the ground and the low voltage node of the corresponding one of the plurality of capacitors; 
 the plurality of series discharging switches is electrically connected in series with the plurality of capacitors; 
 an initial series discharging switch of the plurality of series discharging switches is electrically connected between the input voltage node and the low voltage node of a corresponding initial capacitor of the plurality of capacitors; 
 each remaining series discharging switch of the plurality of series discharging switches is electrically connected between the low voltage node of a corresponding remaining one of the plurality of capacitors and the high voltage node of a previous one of the plurality of capacitors in the series; and 
 the high voltage node of a final one of the plurality of capacitors in the series is electrically connected to the capacitor series output node. 
 
     
     
       3. The method of  claim 1 , wherein:
 the plurality of parallel charging switches and the plurality of series discharging switches have a breakdown voltage of about 3-50 volts to charge the plurality of capacitors to the parallel charged voltage level. 
 
     
     
       4. The method of  claim 1 , wherein
 each of the plurality of capacitors has a high voltage node and a low voltage node; 
 each resistor of the plurality of resistors is electrically connected between the high voltage node of the corresponding one of the plurality of capacitors and a gate node of the corresponding one of the plurality of series discharging switches; 
 the gate-source voltage generated by each resistor of the plurality of resistors deactivates the corresponding one of the plurality of series discharging switches when the plurality of parallel charging switches are activated; and 
 each resistor of the plurality of resistors pulls a gate voltage of the corresponding one of the plurality of series discharging switches to a voltage level of the high voltage node of the corresponding one of the plurality of capacitors to activate the corresponding one of the plurality of series discharging switches when the plurality of parallel charging switches are deactivated. 
 
     
     
       5. The method of  claim 1 , further comprising:
 generating the current through each of the plurality of resistors by activating a corresponding one of a plurality of current source switches when the plurality of parallel charging switches are activated; 
 wherein: 
 each of the plurality of current source switches corresponds to one of the plurality of resistors and to one of the plurality of series discharging switches; 
 each of the plurality of current source switches is electrically connected to the corresponding one of the plurality of resistors at a gate node of the corresponding one of the plurality of series discharging switches; and 
 the plurality of current source switches are deactivated when the plurality of parallel charging switches are deactivated. 
 
     
     
       6. The method of  claim 5 , further comprising:
 activating the plurality of current source switches by generating a gate drive voltage for the plurality of current source switches upon deactivating a grounding switch when the plurality of parallel charging switches are activated; 
 wherein: 
 deactivation of the grounding switch causes a current source and a bias voltage switch to generate the gate drive voltage; 
 the grounding switch is activated when the plurality of parallel charging switches are deactivated; and 
 activation of the grounding switch prevents the generating of the gate drive voltage. 
 
     
     
       7. The method of  claim 1 , further comprising:
 generating, by an output diode, an output capacitor and an output resistor, a charge pump output voltage level from the series capacitor output voltage level; 
 the output diode has an anode electrically connected to the capacitor series output node and a cathode electrically connected to an output voltage node of the charge pump; 
 the output capacitor is electrically connected between the output voltage node and the ground; and 
 the output resistor is electrically connected in parallel with the output capacitor. 
 
     
     
       8. A charge pump comprising:
 a plurality of capacitors; 
 a plurality of parallel charging switches electrically connected to the plurality of capacitors to charge the plurality of capacitors in parallel between an input voltage node and a ground when the plurality of parallel charging switches are activated, the plurality of capacitors being charged to a parallel charged voltage level; 
 a plurality of series discharging switches electrically connected to the plurality of capacitors to generate a series capacitor output voltage level at a capacitor series output node by discharging the plurality of capacitors in series between the input voltage node and the capacitor series output node when the plurality of series discharging switches are activated; and 
 a plurality of resistors, each corresponding to one of the plurality of capacitors and to one of the plurality of series discharging switches; 
 and wherein: 
 the plurality of parallel charging switches are activated when the plurality of series discharging switches are deactivated; and 
 the plurality of series discharging switches are activated when the plurality of parallel charging switches are deactivated. 
 
     
     
       9. The charge pump of  claim 8 , wherein:
 each of the plurality of capacitors has a high voltage node and a low voltage node; 
 the plurality of parallel charging switches includes a plurality of first parallel charging switches and a plurality of second parallel charging switches; 
 each of the plurality of first parallel charging switches corresponds to one of the plurality of capacitors; 
 each of the plurality of first parallel charging switches is electrically connected between the input voltage node and the high voltage node of the corresponding one of the plurality of capacitors; 
 each of the plurality of second parallel charging switches corresponds to one of the plurality of capacitors; 
 each of the plurality of second parallel charging switches is electrically connected between the ground and the low voltage node of the corresponding one of the plurality of capacitors; 
 the plurality of series discharging switches is electrically connected in series with the plurality of capacitors; 
 an initial series discharging switch of the plurality of series discharging switches is electrically connected between the input voltage node and the low voltage node of a corresponding initial capacitor of the plurality of capacitors; 
 each remaining series discharging switch of the plurality of series discharging switches is electrically connected between the low voltage node of a corresponding remaining one of the plurality of capacitors and the high voltage node of a previous one of the plurality of capacitors in the series; 
 the high voltage node of a final one of the plurality of capacitors in the series is electrically connected to the capacitor series output node. 
 
     
     
       10. The charge pump of  claim 8 , wherein:
 the plurality of parallel charging switches and the plurality of series discharging switches have a breakdown voltage of about 3-50 volts to charge the plurality of capacitors to the parallel charged voltage level. 
 
     
     
       11. The charge pump of  claim 8 , wherein:
 each of the plurality of capacitors has a high voltage node and a low voltage node; 
 each resistor of the plurality of resistors is electrically connected between the high voltage node of the corresponding one of the plurality of capacitors and a gate node of the corresponding one of the plurality of series discharging switches; 
 a current through each resistor of the plurality of resistors causes a gate-source voltage of the corresponding one of the plurality of series discharging switches that deactivates the corresponding one of the plurality of series discharging switches when the plurality of parallel charging switches are activated; and 
 each resistor of the plurality of resistors pulls a gate voltage of the corresponding one of the plurality of series discharging switches to a voltage level of the high voltage node of the corresponding one of the plurality of capacitors to activate the corresponding one of the plurality of series discharging switches when the plurality of parallel charging switches are deactivated. 
 
     
     
       12. The charge pump of  claim 8 , further comprising:
 a plurality of current source switches, each corresponding to one of the plurality of resistors and to one of the plurality of series discharging switches, each of the plurality of current source switches being electrically connected to the corresponding one of the plurality of resistors at a gate node of the corresponding one of the plurality of series discharging switches, each of the plurality of current source switches being activated to cause the current through the corresponding one of the plurality of resistors when the plurality of parallel charging switches are activated, and the plurality of current source switches being deactivated when the plurality of parallel charging switches are deactivated. 
 
     
     
       13. The charge pump of  claim 12 , further comprising:
 a current source; 
 a grounding switch electrically connected to the current source; and 
 a bias voltage switch electrically connected to the current source and the grounding switch; 
 and wherein: 
 the grounding switch is deactivated when the plurality of parallel charging switches are activated, and the grounding switch is activated when the plurality of parallel charging switches are deactivated; 
 deactivation of the grounding switch causes the current source and the bias voltage switch to generate a gate drive voltage that activates the plurality of current source switches; and 
 activation of the grounding switch prevents generation of the gate drive voltage. 
 
     
     
       14. The charge pump of  claim 8 , further comprising:
 an output diode having an anode and a cathode, the anode being electrically connected to the capacitor series output node, and the cathode being electrically connected to an output voltage node of the charge pump; 
 an output capacitor electrically connected between the output voltage node and the ground; and 
 an output resistor electrically connected in parallel with the output capacitor; 
 and wherein the output diode, the output capacitor, and the output resistor generate a charge pump output voltage level from the series capacitor output voltage level. 
 
     
     
       15. A charge pump comprising:
 a plurality of capacitors, each having a high voltage node and a low voltage node; 
 a plurality of input diodes and a plurality of charging switches electrically connected to the plurality of capacitors to charge the plurality of capacitors in parallel between an input voltage node and a ground when the plurality of charging switches are activated, the plurality of capacitors being charged to a parallel charged voltage level; 
 a plurality of discharging switches electrically connected to the plurality of capacitors to generate a series capacitor output voltage level at a capacitor series output node by discharging the plurality of capacitors in series between the input voltage node and the capacitor series output node when the plurality of discharging switches are activated; and 
 a plurality of resistors, each corresponding to one of the plurality of capacitors and to one of the plurality of discharging switches, each of the plurality of resistors being electrically connected between the high voltage node of the corresponding one of the plurality of capacitors and a gate node of the corresponding one of the plurality of discharging switches; 
 and wherein: 
 a current through each resistor of the plurality of resistors causes a gate-source voltage of the corresponding one of the plurality of discharging switches that deactivates the corresponding one of the plurality of discharging switches when the plurality of charging switches are activated; and 
 each resistor of the plurality of resistors pulls a gate voltage of the corresponding one of the plurality of discharging switches to a voltage level of the high voltage node of the corresponding one of the plurality of capacitors to activate the corresponding one of the plurality of discharging switches when the plurality of charging switches are deactivated. 
 
     
     
       16. The charge pump of  claim 15 , further comprising:
 a plurality of current source switches, each corresponding to one of the plurality of resistors and to one of the plurality of discharging switches, each of the plurality of current source switches being electrically connected to the corresponding one of the plurality of resistors at the gate node of the corresponding one of the plurality of discharging switches, each of the plurality of current source switches being activated to cause the current through the corresponding one of the plurality of resistors when the plurality of charging switches are activated, and the plurality of current source switches being deactivated when the plurality of charging switches are deactivated. 
 
     
     
       17. The charge pump of  claim 16 , further comprising:
 a current source; 
 a grounding switch electrically connected to the current source; 
 a bias voltage switch electrically connected to the current source and the grounding switch; 
 and wherein: 
 the grounding switch is deactivated when the plurality of charging switches are activated, and the grounding switch is activated when the plurality of charging switches are deactivated; 
 deactivation of the grounding switch causes the current source and the bias voltage switch to generate a gate drive voltage that activates the plurality of current source switches; and 
 activation of the grounding switch prevents generation of the gate drive voltage. 
 
     
     
       18. The charge pump of  claim 15 , further comprising:
 an output diode having an anode and a cathode, the anode being electrically connected to the capacitor series output node, and the cathode being electrically connected to an output voltage node of the charge pump; 
 an output capacitor electrically connected between the output voltage node and the ground; and 
 an output resistor electrically connected in parallel with the output capacitor; 
 and wherein the output diode, the output capacitor, and the output resistor generate a charge pump output voltage level from the series capacitor output voltage level. 
 
     
     
       19. The charge pump of  claim 15 , wherein:
 each of the plurality of input diodes corresponds to one of the plurality of capacitors; 
 each of the plurality of input diodes is electrically connected between the input voltage node and the high voltage node of the corresponding one of the plurality of capacitors; 
 each of the plurality of charging switches corresponds to one of the plurality of capacitors; 
 each of the plurality of charging switches is electrically connected between the ground and the low voltage node of the corresponding one of the plurality of capacitors; 
 the plurality of discharging switches is electrically connected in series with the plurality of capacitors; 
 an initial discharging switch of the plurality of discharging switches is electrically connected between the input voltage node and the low voltage node of a corresponding initial capacitor of the plurality of capacitors; 
 each remaining discharging switch of the plurality of discharging switches is electrically connected between the low voltage node of a corresponding remaining one of the plurality of capacitors and the high voltage node of a previous one of the plurality of capacitors in the series; 
 the high voltage node of a final one of the plurality of capacitors in the series is electrically connected to the capacitor series output node. 
 
     
     
       20. The charge pump of  claim 15 , wherein:
 the plurality of charging switches and the plurality of discharging switches have a breakdown voltage of about 3-50 volts to charge the plurality of capacitors to the parallel charged voltage level.